December 10, 2012

Elk Bones Reveal History Of A Species In Yellowstone Park

Conservationists typically rely on direct observation, whether from the air or the ground, to understand how different species use the land in their habitat, but a new method from a University of Cincinnati professor could give them another way to gain insight into species land use.

According to the November cover article for the Ecological Society of America's journal Ecology, Josh Miller assessed elk habitats use in Yellowstone National Park by studying the bones and antlers that they have left behind. Miller performed the study while working on his doctoral thesis in paleontology at the University of Chicago.

"It turns out that bones are really informative," he said in a statement. "This [research] opened up a completely unexpected opportunity for studying modern ecosystems, particularly for areas where our knowledge of animal populations is more limited."

Determining land use through the study of animal bones hasn´t been practiced before because most researchers believed that bones don't last long enough out in the elements to be of any use. However, Miller has found that some bones can last for hundreds of years and that they can weather in a predictable pattern.

Through the use of radiocarbon dating techniques, Miller was able to better understand how a bone or antler weathered as it aged, and was eventually so familiar with patterns of aging that he can now pick up a bone from the ground and know how long it has aged in the open, from one to 100 years.

By cataloging and studying the elk remains, Miller was able to construct a historical profile of their land use. Miller then checked his calculations against the historical records that were created based on aerial observations.

For example, bull elk typically shed their antlers in late winter. By locating and dating these antlers, Miller was able to understand where the animals have historically foraged for food in the coldest months.

“The capacity of these data to reveal patterns of landscape-use is illustrated here; the spatial distribution of antlers obtained in a few summers describes decadally averaged late-winter landscape use of Yellowstone bull elk with higher fidelity than most individual aerial surveys,” Miller posited in his report.

The scientist was also able to determine typical calving grounds for the elk populations around Yellowstone based on the locations of calf bones. The calf bones also suggest historical patterns of predation around the park.

Miller was also able to track major events in the recent history of the park through his elk bone samples. Based on pattern shifts in a few areas of the park, he was able to detect traces of the devastating wildfires of 1988, the repatriation of grey wolves beginning in 1995, and the resurgence of willows, aspen, and cottonwoods, all of which afford camouflage and shelter for the elk.

Miller said his study allows conservationists to put relatively recent data from direct observation into broader context with long-range planning, helping researchers and conservationists to sort out important changes from the statistical noise created by direct observations.

He also noted that studying the bones is a minimally invasive method for tracking the elk land use patterns, compared to aerial observations.